I have over-dyed a light green cashmere sweater to near black using the spruce acid dye. Guess my surprise. I wonder if I am able to lighten the color using color remover or will that just remove all the color? I do have enough dye to redye it again but I hate abusing my lovely cashmere like this. Also, which product should I use? Any tips on how long to leave the product on (or not)? Any suggestions appreciated!

The heating and cooling is more damaging to the cashmere than the dyeing or color removing itself. You can absolutely remove the color to a small extent by adding less color remover. I would start with 5 grams or so like half a teaspoon if you don't want to totally remove it.

You want to take the garment out as soon as you reach the color you want. So it depends on what you want.